Stock 318 bolt on performance modifications

As I'm pulling parts off this 1975 Valiant 318 to transplant it from a four door parts car to a 72 slant 6 Swinger. I'm wondering if it would be worth it to add headers, intake, and a small four barrel carburetor.

I'm actually fine running the motor as is with the 2 barrel carburetor and stock exhaust. This car is just going to be a cruiser, but if I could increase mileage or Hp noticeably. I have an open mind and a small budget.:D

Any input from the 318 guys? Remember this would just be a couple bolt on items. Were not talking about getting into the engine.